In general, a light emitting diode is fabricated by using a pn junction as a basic structure. Namely, two semiconductors, one controlled to p type, and the other controlled to n type by using dopants, are fabricated, and a structure obtained by joining the semiconductors together is used. In recent years, quantum dots have been dispersed in the pn junction interface or the i layer in a pin junction in order to try to increase luminous efficiency of the light emitting diode having a pn junction as a basic structure.
For example, in Patent Document 1, a light emitting diode in which quantum dots of germanium are dispersed in silicon is proposed and disclosed.
The light emitting device indicates, as shown in FIG. 3, an example of a light emitting diode in which quantum dots of germanium are dispersed in silicon. On an n+ silicon layer 31, a first epitaxial layer 32 is stacked, and quantum dots 35 are formed on the surface. Then, a second epitaxial layer 33 is coated, and further a p+ epitaxial layer is stacked thereon. Thus, a quantum dot-dispersed light emitting diode is configured. Respective layers are formed with epitaxial relation so that the layers are held on the underlayer 31.
The light emitting device is configured such that quantum dots are dispersed in silicon, which is an indirect semiconductor, thereby enhancing the luminous efficiency.
Whereas, Patent Document 2 proposes a light emitting device configured as follows: an i layer is formed on an n layer, and the layer is irradiated with an ion beam and perforated with pores; the pores are filled with a semiconductor having a narrow forbidden band; and then, a p layer is stacked thereon, thereby to fabricate a pin type light emitting diode.
Further, in Patent Document 3, there is also proposed the following method: a group V element different from the group V element of a III-V compound semiconductor is supplied to the III-V compound semiconductor surface, so that substitution occurs between the group V element of the III-V compound semiconductor. The supplied group V element effects strain due to the mismatch of the lattice constant, thereby forming a quantum dot structure. However, even with this method, epitaxial growth is used.
Patent Document 1: Japanese Patent No. 2559999
Patent Document 2: U.S. Pat. No. 6,554,808 B2
Patent Document 3: JP-A-2002-198512